The (Al.sub.y Ga.sub.1-y).sub.0.5 P materials system lattice matched to GaAs substrates is an attractive material for the realization of high performance visible laser diodes. Room temperature cw operation of double heterostructure (DH) laser diodes has been reported by M. Ikeda et al, Appl. Phys. Lett., 47:1027 (1985); by M. Ishikawa et al, Appl. Phys. Lett. 48:207 (1986); and by K. Kobayashi et al, Electron. Lett. 21:931 (1985). To date, DH lasers have shown the lowest threshold current densities, with the best reported value of 1.7 kA/cm.sup.2 for a structure with Al.sub.0.5 In.sub.0.5 P cladding layer (cf M. Ishihawa et al. Extended Abstracts of the 18th (1986 International) Conference on Solid State Devices and Materials. Tokyo. 1986 (Komiyama. Japan. 1986), pp. 153-156)).
However, most laser results have been achieved with quaternary (Al.sub.y Ga.sub.1-y).sub.0.5 P cladding layers which reduce optical confinement but are required to overcome the difficulty of obtaining low-resistivity p-type layers using zinc dopant. The best broad-area laser threshold current densities for structures with quaternary cladding layers are about 3.5 kA/cm.sup.2 (Ishikawa et al, Appl. Phys. Lett., 48:207 (1986) and M. Ikeda et al, Appl. Phys. Lett., 50:1033 (1987)). Efforts to reduce threshold current have included multiquantum well structures which have reduced lasing wavelength but have not had the desired effect of reducing threshold current (of W. T. Tsang, Phys. Lett., 39:134 (1981) and H. Tanaka et al, J. Appl. Phys., 61 1713 (1987)). The present invention provides a unique structure with a single quantum well (QW) active region and separate optical confinement region with enhanced performance.
The new materials represent the first operation of an AlGaInP laser with a single active quantum well and are an advance over double heterostructure (DH) lasers. Using the new material (AlGaInP), high-power results are obtained for both DH and GRIN-SCH laser structures.